Good points, and I certainly agree with not using HTML5 as the umbrella term.
Presumably the aim of the logo is to let (non-developers) know that a site is built with a certain set of technologies?
So the next question is: What should the umbrella term be?
I believe Eric Meyer has been using “Open web stack”, which is accurate and works with developers. However, I think we need something a little shorter and snappier (preferably an acronym of 6 letters or less that can be pronounced easily. Like AJAX.).
Something that combines W3C, open, web… the WOW stack? Maybe not, any other ideas?
We need something else, or HTML5 will become entrenched as the umbrella term.